Hose pumps are used in medical engineering to meter liquids, e.g., to meter water in a breathing air humidifier. Such pumps are also sometimes referred to as peristaltic pumps.
Commercially available hose pumps have d.c. motors with sliding collectors, which operate at relatively high speeds. The service life of these motors is limited and corresponds, at the most, to a continuous operation for less than one year; the costs are rather substantial. Collectorless motors with external commutator are still expensive. For adjustment to the low speeds needed by a hose pump, these motors are provided with a gear, which causes additional friction, associated with wear and loss of power of the motor.
Stepping motors as a drive for hose pumps have a substantially longer service life, because they run at a lower speed and are therefore substantially less expensive than d.c. motors. One drawback of such stepping motors is that they deliver a relatively low torque in relation to their size, so that the use of a stepping motor instead of a geared d.c. motor is not readily possible.
To reduce the friction in a hose pump and to make it possible to use a stepping motor with a relatively low specific torque as a drive motor, a relatively thin-walled, elastic pump hose was tensioned over the pump head, so that the rollers of the pump head close individual segments in the hose, which bring about delivery of the enclosed liquid during the rotation of the pump head. The pretension of the hose determines the maximum delivery head and the maximum pump pressure. The friction, which is caused by this principle, is generated by the friction of the rollers of the pump head and by the inner friction in the hose material.
One drawback of the latter principle of a hose pump arises from the fact that a thin-walled, elastic hose with a usual circular cross section is worn after only a few hours of operation.